Vision system that perform measurement, inspection, alignment of objects and/or decoding of symbology (e.g. bar codes) are used in a wide range of applications and industries. These systems are based around the use of an image sensor, which acquires images (typically grayscale or color, and in one, two or three dimensions) of the subject or object, and processes these acquired images using an on-board or interconnected vision system processor. The processor generally includes both processing hardware and non-transitory computer-readable program instructions that perform one or more vision system processes to generate a desired output based upon the image's processed information. This image information is typically provided within an array of image pixels each having various colors and/or intensities. In the example of a symbology (barcode) reader, the user or automated process acquires an image of an object that is believed to contain one or more barcodes. The image is processed to identify barcode features, which are then decoded by a decoding process and/or processor obtain the inherent alphanumeric data represented by the code.
It is increasingly desirable to provide vision systems and associated vision system components that can be used for a variety of purposes. By way of example, an integrated sensor and single instruction, multiple data (SIMD) processor, which can be termed a vision system on a chip (VSoC), is shown and described in U.S. patent application Ser. No. 12/184,187, entitled VISION SENSORS, SYSTEMS AND METHODS, by E. John McGarry, et al., the teachings of which are incorporated by reference as useful background information. This architecture provided a highly versatile and widely applicable vision system platform for a variety of vision system tasks. The ability to provide a versatile system reduces costs by eliminating the need to provide a number of purpose-built vision system arrangements for specific applications. It is therefore desirable to provide such versatile vision system platforms. Other currently available arrangements of sensors and processors (e.g. digital signal processors (DSPs) can also be employed to provide a relatively compact and robust vision system.
A significant component of many camera systems is the illumination assembly. To adequately acquire an image of an object's surface, it is desirable to illuminate it appropriately. Depending upon the features being imaged and the relative angle of the camera axis to the features, the type of illumination employed can vary. For example, some features (e.g. peened features) can be best imaged using low-angle illumination, while other features (e.g. printed, high-contrast features) are typically best imaged using direct, high-angle illumination. Likewise the wavelength of illumination can vary depending on the nature of the features—that is, some features are best illuminated in the visible range, while others may be enhanced using infrared (IR) or ultraviolet (UV) light. Likewise, for some applications it is desirable to employ polarized light and/or to filter the light entering the camera with a polarizer or other appropriate optical filter. Many camera systems include a ring illumination arrangement consisting of one or more rows of that encircle the camera lens. These illuminators are often fixed in place, constructed on a circuit board, and containing a predetermined number and arrangement of lighting elements, such as LEDs. The illuminator is provided to the system based upon its expected application and is not readily replaced after the system has been delivered. Moreover, the manufacturer may offer systems with a various choices of illuminators in order to provide needed inventory to satisfy a potential customer's needs. Some of these systems may remain in inventory for a long duration before they are sold (if they are sold at all) to a customer/user. This increases the manufacturer's costs and can result in a limited number of available illuminator choices. To meet a specific user's need, the manufacturer may need to produce a custom-designed illuminator that entails further costs and delays in delivering completed vision systems to the user.
Moreover, when a system is delivered with an illumination assembly that proves inadequate, or it is desirable to re-task the system to a different application, it may be challenging or impractical to exchange the attached illuminator with one more suited to the task.
It is therefore desirable to provide an illumination assembly for a vision system that is highly versatile and adaptable to a variety of different applications without the need to maintain a large inventory of completed vision systems. This illumination assembly should be capable of interoperating with a variety of camera lens systems and should allow for exchangeability while avoiding the need of costly changes to the underlying vision system's physical housing or package. Moreover, the illumination assembly should enable a variety of types (wavelengths) of light to be projected, at a variety of angles, and in a wide range of power output levels. In addition, the illumination assembly should allow for use of various filters, to condition the projected illumination and/or to optically filter light received by the camera from the illuminated scene.